Self-clamping fastening ring

ABSTRACT

An elastic fastening ring that can be mounted in a self-clamping manner on a bearing part should have a simple design, a reliable operation and at the same time the function of an axial spring element. For this purpose, the disclosed fastening ring consists of a washer with a sinuous ring-shaped band whose length may be elastically changed in the circumferential direction over its whole radial width.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Use of a meandering washer as a fastening ring.

The invention relates to the use of a meandering washer as a fasteningring having the features of claim 6.

A washer having the subject-matter features of claim 6 is already know,for use as a cup spring, from U.S. Pat. No. 4,680,847.

2. Description of the Relaed Art Including Information Disclosed Under37 C.F.R. 1.97 and 1.98.

Comparable meandering rings in the form of split rings, which can eachbe introduced into an annular groove of a carrier part radially on theinside or outside, with stressing, are known as fasterning rings. Byvirtue of being embedded in a groove, these fastening rings can transmitaxial forces and thus serve as a fastening element for absorbing axialforces. If the intention is to use such a fastening ring to retain afastenable part in a precisely defined manner in the axial direction ona carrier part, in the form for example of a shaft or of a pipe socket,this requires very precise production at one end of the fastenable partin the axial direction between the axial fastening surfaces of said partand the position of the receiving groove, which is to be provided in thecarrier part, for the split fastening ring. Even with extremely preciseproduction, in practice, axially play-free fastening cannot usually beachieved in a sufficiently reliable manner. Furthermore, it is notpossible, using such fastening rings, for a fastenable part to beclamped in with axially acting spring force. In order to achieve aclamping-in action under spring force in the axial direction, it isnecessary, in the case of such fastening rings, for a spring element tobe introduced between the fastening ring and the fastenable part. Such aspring element may be, for example, a cup spring.

Furthermore, closed washers which are serrated over the innercircumference are also known as fastening rings. These washers may bedesigned as cup springs. Such a washer which is closed over itscircumference radially on the outside does not ensure sufficientlyreliable self-clamping for a non-slip fastening position with high axialforces acting on the washer. Moreover, such a washer which is split juston its inner circumference does not permit axial spring stressingforces.

As a fastening element for, for example, a releasable axial connectionof two shafts, use is made, in the prior art, of washers which eachcomprise a meandering annular band, which, closed in the circumferentialdirection, can be changed in length elastically over its entire radialwidth. However, these washers are not used as self-clamping fasteningrings. Those washers only become a fastening element by being introducedin an approximately positively locking manner into an annular gap,formed by the two parts which are to be connected to one another, intwisted form radially on the inside and outside, and then by beingbraced axially. Twisted form in this case means that the annular bandextends in a surface generated by a cone.

By virtue of the annular band being forced in the direction of a planarprogression during axial bracing, the internal diameter decreases with asimultaneous increase in the external diameter. These changes indiameter result in radial bracing between one part, designed as anexternally abutting bushing, and the other part, which as a shaftengages internally, it being the intention for these parts to beconnected to one another. In such a case, the bracing, which is to beapplied axially, takes place, for example, via an adjusting nut actingon one of the two parts which are to be connected.

BRIEF SUMMARY OF THE INVENTION

Taking this as departure point, the invention deals with the problem ofproviding a fastening ring which is of straightforward construction andprovides a reliable grip without additional parts.

A solution for this problem is given by the use of a washer as afastening ring in accordance with the features of claim 1.

The invention is based on the idea of a washer which is elasticallyexpansible in the circumferential direction being pushed, withprestressing, onto or into a carrier part, which may be for example ashaft or a pipe socket.

In the case of a pushing-on operation, the internal diameter isincreased in each case, this resulting in the annular band lengtheningover its entire radial width. This thus produces, within the annularband, circumferential stressing, which results in the annular bandtwisting conically. The twisting effect is brought about in that theradially outer annular-band regions try to assume a position which is asclose as possible to their initial energy state, that is to say theannular band tries to assume a position with the smallest possiblechange in energy with respect to the initial position. The twistingeffect, and thus the conical oblique positioning of the annular band,increases as radial widening of the annular band increases.

The oblique positioning of the annular band, which is brought about bythe twisting, thus has its origins in the resiliently actingcircumferential force which is produced in the circumference of theannular band by the latter being widened. This means, in turn, that itis possible to change the oblique positioning of the annular band by theaxial application of force, a spring force which emanates axially fromthe annular band being produced in the process. In this case, the springforce emanates from the circumferential force from the elasticdeformation of the annular band. It is thus possible to set the springforce by the increase in diameter when the washer is pushed onto acarrier part. This means that, depending on radial prestressing, it ispossible to use the same fastening ring according to the invention torealize springs which act differently in the axial direction. The samegoes analogously for a fastening ring according to the invention whichis clamped in a sleeve.

The fastening ring according to the invention thus provides a fasteningmeans which, with secure axial fixing on a carrier part, simultaneouslyacts as an axial spring with a spring force which can be preset. As aresult, fastenable parts can be braced axially by such a ring. Thisconstitutes a considerable advantage since, for this purpose, there isno need for any additional part, as in the case of the split fasteningrings, the so-called spring rings, of the prior art described in theintroduction.

In the case of the fastening rings according to the invention, it isexpedient for these to be designed with an oblique, conically runningannular band even in the initial state. This reliably defines inadvance, in a straightforward manner, in which direction twisting of theannular band will take place in the event of lengthening or shortening.

With regard to twisting, washers have a so-called centre point ofinversion within the radial cross-section of the annular band, thecircumferential stressing emanating from said centre point as a radiallyacting force. In practice, the centre point of inversion S is thus thecentre point of force which is critical for the radial stressing whichemanates from the annular element. If this centre point of force islocated outside the radial abutment surface of the annular band againstan associated carrier part, there is a moment which gives the washer anaxially acting spring force.

A washer which runs conically in the stressed state may be deformed withthe axial application of force, into a planar state counter to an axialspring force produced by the annular band. If, in such a planar state,the annular band butts, radially on the outside or inside, in fullsurface contact against a carrier part over its entire height, then thecentre point of inversion is likewise located in the region of theannular-band plane, to be precise approximately halfway up the axialheight of the resilient band. As a result, there can be no spring momentin such a position, that is to say in such a position the washer doesnot have any axial spring force. In order to avoid this, the radiallyinner or outer abutment surface of the annular band is to be configuredsuch that there is an active spring moment in each case within apredeterminable twisting range, including a planar extent of the annularband. This can be achieved in that the radial abutment surfaces achievecorresponding oblique positioning with respect to the radial extent ofthe annular band. Such a configuration of the radial annularbandcircumferential surfaces also makes it possible to achieve, inparticular, a kind of linear contact with respect to the carrier part onwhich the washer is braced. Such linear contact increases the resistanceagainst displacement of the washer in the axial direction, thisadvantageously improving the functional reliability of the fasteningring.

The fastening ring according to the invention provides, overall, astraightforward fastening element which can be fixed securely in theaxial direction and additionally has the great advantage ofsimultaneously constituting an axially acting spring with a spring forcewhich can be set depending on the radial prestressing in each case. Thisspring action makes it possible, even if the fastenable part has notbeen produced particularly precisely in the axial direction, to haveaxially play-free fixing, in practice, with the axial spring force beingutilized in the process. In a fair number of cases, axially resilientmounting is even desired or, in part, also necessary. This applies, forexample, when a fastenable part changes in its axial length by heatexpansion at varying temperatures. In such cases, it is also desirableto have resilient follow-up stressing, in which a fastenable part isforced against a seal, with stressing, by the fastening ring and thematerial of this seal, over the course of time, undergoes plasticdeformation in the direction of axial shortening.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

An exemplary embodiment is illustrated in the drawing, in which:

FIG. 1 shows a plan view of an elastic fastening ring with a meanderingannular band,

FIG. 2 shows a section through the fastening ring along line II--II inFIG. 1, with abutment against a cylindrical carrier part beingindicated,

FIG. 3a shows a detail in accordance with the circle III in FIG. 2 withforces depicted,

FIG. 3b shows the detail according to FIG. 3a with an "angled"annular-band cross-section.

DETAILED DESCRIPTION OF THE INVENTION

A fastening ring 1 comprises a meandering annular band 2 which can bedeformed elastically in the circumferential direction. The material ofthe annular band 2 is, for example, a spring steel.

In the non-stressed, initial position of the fastening ring 1, theannular band 2 is oriented conically. This cone angle is indicated inFIG. 2 by a. This angle may be of a magnitude of, for example, between 0and 45 .

In order for it to be possible for a fastening part 3, which may be forexample a plate, to be fixed in an axially play-free manner, with springstressing, on a carrier part 4, which may be for example a spindle withan annular collar 5, the fastening ring 1 is drawn onto the cylindricalpart of the carrier part 4 with expansion in the circumferentialdirection. During this drawing-on operation of the fastening ring 1, theannular band 2 twists in the direction of a relatively pronouncedoblique position, which is indicated in FIG. 2 by the angle b, andconstitutes the cone angle in the installed state, and is thus greaterthan the initial angle a. Thereafter, the fastening ring 1 is forcedagainst the fastening part 3 with the application of axial force, inwhich case the annular band 2 is twisted back, in the direction of apronounced axial spring action, to a cone angle g, which, in magnitude,is between the initial angle a and the cone angle b of the fasteningring 1 which is only expanded but is not loaded in the axial direction.

The difference between angles b and g gives the prestressed springcompensating excursion in the axial direction, via which axial follow-upstressing is possible if an elastic seal 6 provided in the annularcollar 5 should, over the course of time, shorten axially under plasticdeformation.

FIG. 3a illustrates, in a section through a web of an annular band 2,said annular band 2 butting against a carrier part 4 in a radiallyexpanded manner. S indicates the position of the centre point ofinversion of this annular-band cross-section. In practice, this is thecentre point of force of the annular-band cross-section through whichthe circumferential stressing force runs. A radial force component Femanates from this point. A moment M acts in terms of the abutment ofthe annular band 2 against the carrier part 4. This moment M counteractsan axial abutment force A, emanating from the annular band 5, as springforce.

An increased spring moment M can be achieved by a "bent" annular-bandshape, as is depicted in FIG. 3b, since in this case, with the sameoverall radial and axial extent of the fastening ring 1, the centrepoint of inversion "S" is at an increased axial distance away from theradially inner abutment surface against the carrier part 4. This resultsin turn, in the axial direction, in an increased lever arm for producingthe spring moment M. The radial spacing of the centre point of inversion"S" remains virtually unchanged in the bent form, as does thus also thelever arm which acts in this direction in relation to a moment.

The radially inner abutment surface 7 of the annular band 2 is designedat an acute angle d with respect to the plane of the annular band 2.This maintains a resiliently acting moment M even in the case of aplanar orientation of the annular band 2, parallel to the abutmentsurface of the annular collar 5. Furthermore, such an angled abutmentsurface 7 ensures linear abutment of the annular band 2 against thecarrier part 4.

A fastening ring according to the invention can thus achieve thefollowing particularly prominent advantages and effects.

The application of an axial force A on the outer circumference of afastening ring 1 drawn, with expansion, onto a spindle, as carrier part,decreases the twisted position (conicity) of the annular band 2 of thestressed fastening ring 1. This results, in turn, in radial widening ofthe circle of the centre points of inversion of the annular band 2, i.e.the centre points of inversion S of the annular-band cross-sections moveradially outwards. This causes an increased radial force of thefastening ring 1, by means of which the latter butts against a spindle,as carrier part 4.

A force A acting in the axial direction on the external diameter of afastening ring 1 which has been drawn onto a spindle, as carrier part 4,produces over approximately the width of the annular band 2, as a leverarm, a moment in the right-hand direction. A moment in the left-handdirection, in contrast, is produced in the annular band 2 by an abutmentreaction force passing from the carrier part 4 to the annular band 2.Disregarding the intrinsic angular momentum of the web cross-sections ofthe annular band, the two moments are in equilibrium.

The radial stiffness of the fastening ring 1 can be predetermined bysuitable dimensioning of the meandering annular band 2.

A specific selection of the radially inner abutment region of theannular band 2 against the carrier part 4 makes it possible topredetermine the length of the lever arm running parallel to the axis ofthe fastening ring 1 (distance between the radial abutment region andcentre point of inversion of the annular band 2).

The length of the lever arm running parallel to the axis of thefastening ring 1 can also be influenced by specific shaping of theannular-band cross-section (for example radial bending).

In the case of a fastening ring 1 drawn onto a carrier part 4, the threelast-mentioned measures can influence within wide limits, in a giveninstallation situation, the force acting on the external diameter in thedirection of the axis of the fastening ring 1. These three measures makeit possible, with axial displacement of the external diameter, for alarge number of different spring characteristics to be realized for theaxial spring action of the fastening ring 1.

Although the drawing depicts just one embodiment, in which the fasteningring 1 has been clamped onto a cylindrical part, this fastening ring 1may also be clamped into a sleeve with the same effect. All that isrequired in this case is for the relationships "radially inside andoutside" to be changed round.

What is claimed is:
 1. Use of a washer made of a meandering annularband, which is closed in the circumferential direction and can bechanged in length in this circumferential direction over its entireradial width, as a fastening ring which butts against a carrier partwith radial, and axial self-clamping wherein when said band isinstalled, at least one oL its circumferential surfaces, and at leastone of its faces are in each case unsupported.
 2. Use of a washeraccording to claim 1, in the case of which, in the non-stresses state,the annular band of the washer runs conically.
 3. Use of a washeraccording to claim 1, in the case of which the respective abutmentsurface of the annular band, said abutment surface coming to be locatedagainst a carrier part with radial stressing, is angled with respect tothe annular-band plane such that the abutment against the carrier partalways takes place, within a twisting range which can be predeterminedfor the annular band, outside a plane defined by the circle of thecenter points of inversion of the annular band.
 4. Use of a washeraccording to claim 1, in the case of which, in a predeterminabletwisting range, the annular band butts against a carrier partessentially linearly.
 5. Use of a washer according to claim 1, in thecase of which the washer-like cross-section of the annular band, locatedin the radial planes of the fastening ring, is bent, with the effect ofan axial increase in the distance between the crosssectional centerpoint of inversion and the abutment provided radially against a carrierpart.